1. Field of the Invention
The present invention relates to a method and apparatus for producing an animation to represent in a quasi fashion the movement of a group including a plurality of members such as persons or animals, and more particularly, to a method and apparatus for controlling the movements of members as a group. The present invention also relates to an entertainment apparatus using such a method.
2. Description of the Related Art
Conventional computer graphic techniques can be classified into two categories: group animation and physically based animation.
Physically based animation refers to an animation which is produced in accordance with a physical principle such as a law of mechanics. More specifically, equations of motion (simultaneous nonlinear equations or differential equations) is determined according to Newton's law or Lagrange's law for each member. However, the cost of precisely simulating mechanical or physical motion is high. Therefore, in the art of information processing apparatuses, such as computers, or in the art of entertainment apparatuses, to which the present invention is applied, some simplification is generally performed to reduce the cost.
That is, in these fields of technologies, it is not necessary to build a physically accurate model, but equations of motion based on a quasi-physical model may be employed if the equations allow the motion of the respective members of interest to be determined in real time and if the resultant motion appears sufficiently natural.
(1) Group Animation to Represent Group Behavior
The research work by Reynolds has had a profound impact upon the art (C. W. Reynolds, “Flocks, Herds, and Schools: A Distributed Behavioral Model”, Proceedings of Siggraph 87, July, 1987, 25-34). After his research work, animation of a group of birds, fishes, or animals can be realized by means of programming independent members of the group. By adjusting parameters associated with the behavior of each member, it is possible to control the behavior in a discrete fashion. However, when the group is viewed as a whole, most of the group behavior occurs spontaneously.
Tu and Terzopoulos have produced a more realistic animation of a group including a plurality of members by improving the reality of the group and the senses by simulating biomechanical behavior (X. Tu and D. Terzopoulos, “Artificial Fishes: Physics, Locomotion, Perception, and Behavior”, Proceedings of Siggraph 94, July, 1994, 24-29). This pioneering research work indicated that the behavior of a group of fishes or animals can be synthesized in a more natural fashion by employing a combination of stimulus-response rules.
Receiving a stimulus from artificial intelligence technology, Funge, Tu, and Terzopoulos have proposed and demonstrated a very elegant framework which allows the representation of perceptive behaviors of members of a group (J. Funge, X. Tu, and D. Terzopoulos, “Cognitive Modeling: Knowledge, Reasoning and Planning for Intelligent Characters”, Proceedings of Siggraph 99, July 1994, 29-38). They have attained their objective in that artificial life and the behavior thereof are animated.
(2) Dynamic and Physical Group Animation
Dynamic and physical animation has great problems in stability and controllability. The problems become serious when groups include a large number of members. The motion of group members is very complicated, and it has been thought that it is very difficult to mathematically represent the complicated motion. However, two physicists, Toner and Tu, have recently explained using a mathematical model how coordinated group behavior occurs spontaneously (J. Toner and Y. Tu, “Flocks, herds, and schools: A Quantitative Theory of Flocking”, Physical Review Letters, Vol. 58, 1999). A profound understanding of the motion of a group including a plurality of members is important. In particular, in the art of computer animation, the development a high-efficiency method of dynamically controlling a group including a plurality of members is required.
Brogan and Hodgins have investigated the behavior of a group with significant dynamics and have presented their opinion about the complexity of the problem (D. Brogan and J. Hodgins, “Group Behaviors for Systems with Significant Dynamics”, Proceedings of the 1995 IEEE/RSJ International Conference on Intelligent Robots and Systems, Vol. 4, 528-534; D. Brogan and J. Hodgins. “Group Behaviors for Systems with Significant Dynamics”, Autonomous Robots 4(1), 1997, pp. 137-153). That is, they have pointed out that motion of individual members and local interactions make it difficult to control the group as a whole and that a combination of local knowledge and global knowledge is required to efficiently control the individual members.
The objective of the research work by Brogan and Hodgins was not to provide a technique for animation but to provide a technique which may be applied to the art of robotics in which realistic equations of motion can be employed so that a realistic group behavior is represented by means of dynamic control. Therefore, this technique is not assumed to be applied to technical fields such as animation in which it is required to simplify the motion of the individual members, depending upon the specific purpose.
Furthermore, in the conventional techniques described above, control factors are adjusted experimentally and manually, and automatic adjustment of the control factors has not yet been achieved.